1. Field of the Invention:
The present invention relates to an operation time control apparatus for electric appliances, for example, an air condition or an refrigerator-freezer.
2. Prior Art
In general, a modern type air conditioner employs at least two timers, a first timer for prevention of reenergization of a compressor for a predetermined short time, such as 3 minutes from a stopping, and a second time, such as 8 minutes, for restarting of the compressor to avoid discomfort from gradual increase of humidity when temperature rise is very slow. To elucidate more in detail about such operation:
Immediately after a stopping the compressor has a very high back-pressure. Therefore, if a compressor motor is energized immediately after a stopping, such high back-pressure hinders the rotation of the motor thereby causing a harmful overloading sometimes leading to a burning of the compressor motor. In order to avoid such inconvenience, there has been a need to provide a mean to prevent a restoration of operation of the compressor immediately after a stopping. This is the reason to necessitate the first timer.
The reason to necessitate the second timer is as follows:
By operation of the compressor motor, the temperature and the moisture of the room air decreases. Then, at a detection of lowering the room temperature beneath a predetermined temperature, the compressor is stopped by the function of the thermostat. Then, both the temperature and the moisture increase. Generally speaking, moisture reaches an unpleasant range faster than temperature's reaching an unpleasant range. However, the thermostat makes the compressor start by detection of only a temperature rise, and therefore, the atmosphere in the airconditioned room becomes uncomfortably moist prior to a restoration of operation of the compressor by means of the thermostat. In order to avoid such inconvenience, there has been a need to provide a measure to restore the compressor motor prior to a detection of the predetermined temperature by the thermostat when a pausing of the compressor lasts longer than a predetermined period. For such reason the second timer is used.
Hitherto, for the abovementioned purpose, two timer circuits, each comprising a timing capacitor and a timing resistor, have been employed. Since the capacitor and resistor of such timer circuit should be of high accuracy, the providing of the two timer circuits causes an increase of cost.